/**
 * wht-md5 - 轻量级MD5加密工具
 * @typedef {Object} WhtMd5Options
 * @property {boolean} [uppercase=false] - 是否输出大写结果
 * @property {number} [iterations=1] - 加密次数，范围1-10
 * @property {number} [length=32] - 输出长度，可选16或32
 */

/**
 * MD5加密函数
 * @param {string} string - 要加密的字符串
 * @param {WhtMd5Options} [options] - 配置选项
 * @returns {string} 加密后的字符串
 */
function md5(string, options = {}) {
    /**
     * 左旋转函数
     * @param {number} lValue - 要旋转的数值
     * @param {number} iShiftBits - 旋转位数
     * @returns {number} 旋转后的数值
     */
    function md5_RotateLeft(lValue, iShiftBits) {
        return (lValue << iShiftBits) | (lValue >>> (32 - iShiftBits));
    }

    /**
     * 无符号加法函数
     * @param {number} lX - 加数1
     * @param {number} lY - 加数2
     * @returns {number} 和
     */
    function md5_AddUnsigned(lX, lY) {
        var lX4, lY4, lX8, lY8, lResult;
        lX8 = (lX & 0x80000000);
        lY8 = (lY & 0x80000000);
        lX4 = (lX & 0x40000000);
        lY4 = (lY & 0x40000000);
        lResult = (lX & 0x3FFFFFFF) + (lY & 0x3FFFFFFF);
        if (lX4 & lY4) {
            return (lResult ^ 0x80000000 ^ lX8 ^ lY8);
        }
        if (lX4 | lY4) {
            if (lResult & 0x40000000) {
                return (lResult ^ 0xC0000000 ^ lX8 ^ lY8);
            } else {
                return (lResult ^ 0x40000000 ^ lX8 ^ lY8);
            }
        } else {
            return (lResult ^ lX8 ^ lY8);
        }
    }

    /**
     * F函数
     * @param {number} x - 输入x
     * @param {number} y - 输入y
     * @param {number} z - 输入z
     * @returns {number} 输出
     */
    function md5_F(x, y, z) {
        return (x & y) | ((~x) & z);
    }

    /**
     * G函数
     * @param {number} x - 输入x
     * @param {number} y - 输入y
     * @param {number} z - 输入z
     * @returns {number} 输出
     */
    function md5_G(x, y, z) {
        return (x & z) | (y & (~z));
    }

    /**
     * H函数
     * @param {number} x - 输入x
     * @param {number} y - 输入y
     * @param {number} z - 输入z
     * @returns {number} 输出
     */
    function md5_H(x, y, z) {
        return (x ^ y ^ z);
    }

    /**
     * I函数
     * @param {number} x - 输入x
     * @param {number} y - 输入y
     * @param {number} z - 输入z
     * @returns {number} 输出
     */
    function md5_I(x, y, z) {
        return (y ^ (x | (~z)));
    }

    /**
     * FF函数
     * @param {number} a - 输入a
     * @param {number} b - 输入b
     * @param {number} c - 输入c
     * @param {number} d - 输入d
     * @param {number} x - 输入x
     * @param {number} s - 输入s
     * @param {number} ac - 输入ac
     * @returns {number} 输出
     */
    function md5_FF(a, b, c, d, x, s, ac) {
        a = md5_AddUnsigned(a, md5_AddUnsigned(md5_AddUnsigned(md5_F(b, c, d), x), ac));
        return md5_AddUnsigned(md5_RotateLeft(a, s), b);
    }

    /**
     * GG函数
     * @param {number} a - 输入a
     * @param {number} b - 输入b
     * @param {number} c - 输入c
     * @param {number} d - 输入d
     * @param {number} x - 输入x
     * @param {number} s - 输入s
     * @param {number} ac - 输入ac
     * @returns {number} 输出
     */
    function md5_GG(a, b, c, d, x, s, ac) {
        a = md5_AddUnsigned(a, md5_AddUnsigned(md5_AddUnsigned(md5_G(b, c, d), x), ac));
        return md5_AddUnsigned(md5_RotateLeft(a, s), b);
    }

    /**
     * HH函数
     * @param {number} a - 输入a
     * @param {number} b - 输入b
     * @param {number} c - 输入c
     * @param {number} d - 输入d
     * @param {number} x - 输入x
     * @param {number} s - 输入s
     * @param {number} ac - 输入ac
     * @returns {number} 输出
     */
    function md5_HH(a, b, c, d, x, s, ac) {
        a = md5_AddUnsigned(a, md5_AddUnsigned(md5_AddUnsigned(md5_H(b, c, d), x), ac));
        return md5_AddUnsigned(md5_RotateLeft(a, s), b);
    }

    /**
     * II函数
     * @param {number} a - 输入a
     * @param {number} b - 输入b
     * @param {number} c - 输入c
     * @param {number} d - 输入d
     * @param {number} x - 输入x
     * @param {number} s - 输入s
     * @param {number} ac - 输入ac
     * @returns {number} 输出
     */
    function md5_II(a, b, c, d, x, s, ac) {
        a = md5_AddUnsigned(a, md5_AddUnsigned(md5_AddUnsigned(md5_I(b, c, d), x), ac));
        return md5_AddUnsigned(md5_RotateLeft(a, s), b);
    }

    /**
     * 转换字符串为字节数组
     * @param {string} string - 输入字符串
     * @returns {Array<number>} 字节数组
     */
    function md5_ConvertToWordArray(string) {
        var lWordCount;
        var lMessageLength = string.length;
        var lNumberOfWords_temp1 = lMessageLength + 8;
        var lNumberOfWords_temp2 = (lNumberOfWords_temp1 - (lNumberOfWords_temp1 % 64)) / 64;
        var lNumberOfWords = (lNumberOfWords_temp2 + 1) * 16;
        var lWordArray = Array(lNumberOfWords - 1);
        var lBytePosition = 0;
        var lByteCount = 0;
        while (lByteCount < lMessageLength) {
            lWordCount = (lByteCount - (lByteCount % 4)) / 4;
            lBytePosition = (lByteCount % 4) * 8;
            lWordArray[lWordCount] = (lWordArray[lWordCount] | (string.charCodeAt(lByteCount) << lBytePosition));
            lByteCount++;
        }
        lWordCount = (lByteCount - (lByteCount % 4)) / 4;
        lBytePosition = (lByteCount % 4) * 8;
        lWordArray[lWordCount] = lWordArray[lWordCount] | (0x80 << lBytePosition);
        lWordArray[lNumberOfWords - 2] = lMessageLength << 3;
        lWordArray[lNumberOfWords - 1] = lMessageLength >>> 29;
        return lWordArray;
    }

    /**
     * 转换字节数组为十六进制字符串
     * @param {number} lValue - 输入字节数组
     * @returns {string} 十六进制字符串
     */
    function md5_WordToHex(lValue) {
        var WordToHexValue = "",
            WordToHexValue_temp = "",
            lByte, lCount;
        for (lCount = 0; lCount <= 3; lCount++) {
            lByte = (lValue >>> (lCount * 8)) & 255;
            WordToHexValue_temp = "0" + lByte.toString(16);
            WordToHexValue = WordToHexValue + WordToHexValue_temp.substr(WordToHexValue_temp.length - 2, 2);
        }
        return WordToHexValue;
    }

    /**
     * 单次MD5加密
     * @param {string} string - 输入字符串
     * @param {number} length - 输出长度
     * @returns {string} 加密后的字符串
     */
    function singleMd5(string, length) {
        var x = Array();
        var k, AA, BB, CC, DD, a, b, c, d;
        var S11 = 7,
            S12 = 12,
            S13 = 17,
            S14 = 22;
        var S21 = 5,
            S22 = 9,
            S23 = 14,
            S24 = 20;
        var S31 = 4,
            S32 = 11,
            S33 = 16,
            S34 = 23;
        var S41 = 6,
            S42 = 10,
            S43 = 15,
            S44 = 21;

        string = string.toString();
        x = md5_ConvertToWordArray(string);
        a = 0x67452301;
        b = 0xEFCDAB89;
        c = 0x98BADCFE;
        d = 0x10325476;

        for (k = 0; k < x.length; k += 16) {
            AA = a;
            BB = b;
            CC = c;
            DD = d;
            a = md5_FF(a, b, c, d, x[k + 0], S11, 0xD76AA478);
            d = md5_FF(d, a, b, c, x[k + 1], S12, 0xE8C7B756);
            c = md5_FF(c, d, a, b, x[k + 2], S13, 0x242070DB);
            b = md5_FF(b, c, d, a, x[k + 3], S14, 0xC1BDCEEE);
            a = md5_FF(a, b, c, d, x[k + 4], S11, 0xF57C0FAF);
            d = md5_FF(d, a, b, c, x[k + 5], S12, 0x4787C62A);
            c = md5_FF(c, d, a, b, x[k + 6], S13, 0xA8304613);
            b = md5_FF(b, c, d, a, x[k + 7], S14, 0xFD469501);
            a = md5_FF(a, b, c, d, x[k + 8], S11, 0x698098D8);
            d = md5_FF(d, a, b, c, x[k + 9], S12, 0x8B44F7AF);
            c = md5_FF(c, d, a, b, x[k + 10], S13, 0xFFFF5BB1);
            b = md5_FF(b, c, d, a, x[k + 11], S14, 0x895CD7BE);
            a = md5_FF(a, b, c, d, x[k + 12], S11, 0x6B901122);
            d = md5_FF(d, a, b, c, x[k + 13], S12, 0xFD987193);
            c = md5_FF(c, d, a, b, x[k + 14], S13, 0xA679438E);
            b = md5_FF(b, c, d, a, x[k + 15], S14, 0x49B40821);
            a = md5_GG(a, b, c, d, x[k + 1], S21, 0xF61E2562);
            d = md5_GG(d, a, b, c, x[k + 6], S22, 0xC040B340);
            c = md5_GG(c, d, a, b, x[k + 11], S23, 0x265E5A51);
            b = md5_GG(b, c, d, a, x[k + 0], S24, 0xE9B6C7AA);
            a = md5_GG(a, b, c, d, x[k + 5], S21, 0xD62F105D);
            d = md5_GG(d, a, b, c, x[k + 10], S22, 0x2441453);
            c = md5_GG(c, d, a, b, x[k + 15], S23, 0xD8A1E681);
            b = md5_GG(b, c, d, a, x[k + 4], S24, 0xE7D3FBC8);
            a = md5_GG(a, b, c, d, x[k + 9], S21, 0x21E1CDE6);
            d = md5_GG(d, a, b, c, x[k + 14], S22, 0xC33707D6);
            c = md5_GG(c, d, a, b, x[k + 3], S23, 0xF4D50D87);
            b = md5_GG(b, c, d, a, x[k + 8], S24, 0x455A14ED);
            a = md5_GG(a, b, c, d, x[k + 13], S21, 0xA9E3E905);
            d = md5_GG(d, a, b, c, x[k + 2], S22, 0xFCEFA3F8);
            c = md5_GG(c, d, a, b, x[k + 7], S23, 0x676F02D9);
            b = md5_GG(b, c, d, a, x[k + 12], S24, 0x8D2A4C8A);
            a = md5_HH(a, b, c, d, x[k + 5], S31, 0xFFFA3942);
            d = md5_HH(d, a, b, c, x[k + 8], S32, 0x8771F681);
            c = md5_HH(c, d, a, b, x[k + 11], S33, 0x6D9D6122);
            b = md5_HH(b, c, d, a, x[k + 14], S34, 0xFDE5380C);
            a = md5_HH(a, b, c, d, x[k + 1], S31, 0xA4BEEA44);
            d = md5_HH(d, a, b, c, x[k + 4], S32, 0x4BDECFA9);
            c = md5_HH(c, d, a, b, x[k + 7], S33, 0xF6BB4B60);
            b = md5_HH(b, c, d, a, x[k + 10], S34, 0xBEBFBC70);
            a = md5_HH(a, b, c, d, x[k + 13], S31, 0x289B7EC6);
            d = md5_HH(d, a, b, c, x[k + 0], S32, 0xEAA127FA);
            c = md5_HH(c, d, a, b, x[k + 3], S33, 0xD4EF3085);
            b = md5_HH(b, c, d, a, x[k + 6], S34, 0x4881D05);
            a = md5_HH(a, b, c, d, x[k + 9], S31, 0xD9D4D039);
            d = md5_HH(d, a, b, c, x[k + 12], S32, 0xE6DB99E5);
            c = md5_HH(c, d, a, b, x[k + 15], S33, 0x1FA27CF8);
            b = md5_HH(b, c, d, a, x[k + 2], S34, 0xC4AC5665);
            a = md5_II(a, b, c, d, x[k + 0], S41, 0xF4292244);
            d = md5_II(d, a, b, c, x[k + 7], S42, 0x432AFF97);
            c = md5_II(c, d, a, b, x[k + 14], S43, 0xAB9423A7);
            b = md5_II(b, c, d, a, x[k + 5], S44, 0xFC93A039);
            a = md5_II(a, b, c, d, x[k + 12], S41, 0x655B59C3);
            d = md5_II(d, a, b, c, x[k + 3], S42, 0x8F0CCC92);
            c = md5_II(c, d, a, b, x[k + 10], S43, 0xFFEFF47D);
            b = md5_II(b, c, d, a, x[k + 1], S44, 0x85845DD1);
            a = md5_II(a, b, c, d, x[k + 8], S41, 0x6FA87E4F);
            d = md5_II(d, a, b, c, x[k + 15], S42, 0xFE2CE6E0);
            c = md5_II(c, d, a, b, x[k + 6], S43, 0xA3014314);
            b = md5_II(b, c, d, a, x[k + 13], S44, 0x4E0811A1);
            a = md5_II(a, b, c, d, x[k + 4], S41, 0xF7537E82);
            d = md5_II(d, a, b, c, x[k + 11], S42, 0xBD3AF235);
            c = md5_II(c, d, a, b, x[k + 2], S43, 0x2AD7D2BB);
            b = md5_II(b, c, d, a, x[k + 9], S44, 0xEB86D391);
            a = md5_AddUnsigned(a, AA);
            b = md5_AddUnsigned(b, BB);
            c = md5_AddUnsigned(c, CC);
            d = md5_AddUnsigned(d, DD);
        }

        var result = (md5_WordToHex(a) + md5_WordToHex(b) + md5_WordToHex(c) + md5_WordToHex(d)).toLowerCase();
        if (length === 16) {
            result = result.substring(0, 16);
        }
        return result;
    }

    // 验证和规范化选项
    options = {
        uppercase: false,
        iterations: 1,
        length: 32,
        ...options
    };

    // 验证长度选项
    if (![16, 32].includes(options.length)) {
        throw new Error('Length must be 16 or 32');
    }

    // 限制加密次数
    options.iterations = Math.min(Math.max(1, options.iterations), 10);

    // 检查参数
    if (typeof string !== 'string') {
        throw new Error('Input must be a string');
    }
    
    let result = string;
    for (let i = 0; i < options.iterations; i++) {
        result = singleMd5(result, options.length);
    }

    // 转换大小写
    return options.uppercase ? result.toUpperCase() : result;
}

/**
 * 创建一个预设选项的MD5加密函数
 * @param {WhtMd5Options} options - 预设的配置选项
 * @returns {function(string): string} 预设配置的MD5加密函数
 */
md5.withOptions = function(options = {}) {
    return function(string) {
        return md5(string, options);
    };
};

export default md5;
